Isophorone diisocyanate based flexible polyurethane foams and fire

Resumen

The aim of the thesis was to synthesize a good performance flame retardant flexible polyurethane (PUR) foam, with the novelty of using isophorone diisocyanate instead of the more commonly used aromatic isocyanates. Nowadays, more than 90% of polyurethanes are produced from aromatic polyisocyanates such as toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI) as they give polyurethanes good mechanical properties. However, their drawback is that they release carcinogenic aromatic diamines in their hydrolytic degradation. Hence, motivated by the desire to solve this problem, aliphatic isophorone diisocyanate (IPDI) based flexible polyurethane foams were synthesized in this work.In order to achieve this objective, the work was divided into different phases as described in the following chapters:Chapter 2 was focused on the synthesis and characterization of a flexible PUR foam that was the starting formulation for the incorporation of different flame retardants. The chemical reactions occurring during the foam generation process were monitored in situ by Attenuated Total Reflectance (ATR)-infrared spectroscopy while the physical changes such as pressure, foam height and dielectric polarization were monitored by the FOAM software (FOAMAT).Chapter 3 was devoted to the final foam chemical and physical characterization in order to determine the foam type. Chemical characterization was carried out by solid nuclear magnetic resonance and ATR while the morphology was determined using atomic force microscopy. The cellular structure was evaluated by means of scanning electron microscopy, optical microscopy using image analysis and tomographic imaging. Moreover, the density was measured along the foams following the ASTM D1662-98 standard, and in order to determine the mechanical properties of the reference foam compression strength tests were performed. Finally, thermal properties evaluation was made based on thermogravimetric analysis. Chapter 4 was centered on the synthesis and characterization of flame retardant containing foams. For this purpose, different reactive flame retardants were introduced into the polymer structure and others included in the formulation as additives. In addition, a flame retardant coating was prepared to cover the reference foam. Then, the synthesized foams were characterized following some of the procedures described in chapter 3 and their fire behavior evaluated by means of the cone calorimeter and NBS smoke density chamber-FTIR techniques. Chapter 5 summarized the most relevant conclusions of the work.